1. Field of the Invention
The present invention relates to providing improved formulations for use in integrated circuit manufacture, particularly improved photoresist and antireflective coating compositions. Preferred methods of the invention include filtration of such formulations with a small mean pore size (e.g. <0.4 or 0.04 micron) filter, particularly a polyamide filter, prior to use of the composition.
2. Background
Photoresists are photosensitive films used for transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable reagents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For a positive-acting photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less developer soluble.
Reflection of activating radiation used to expose a photoresist often poses limits on resolution of the image patterned in the photoresist layer. Reflection of radiation from the substrate/photoresist interface can produce spatial variations in the radiation intensity in the photoresist, resulting in non-uniform photoresist linewidth upon development.
One approach used to reduce the problem of reflected radiation has been the use of an organic radiation absorbing layer interposed between the substrate surface and the photoresist coating layer. See, for example, PCT Application WO 90/03598, EPO Application No. 0 639 941 A1 and U.S. Pat. Nos. 4,910,122; 4,730,405; 4,362,809; and 5,939,236. Such organic underlayers have also been referred to as antireflective layers or antireflective compositions. See also U.S. Pat. Nos. 5,939,236; 5,886,102; 5,851,738; and 5,851,730, all assigned to the Shipley Company, which disclose highly useful antireflective compositions.
While currently available photoresists and antireflective compositions are suitable for many applications, current resists also can exhibit significant shortcomings, particularly in high performance applications such as e.g. formation of highly resolved sub-micron and sub-quarter micron features.
Among other things, particularly problematic are various defects that may occur through lithographic processing, such as pinholes in photoresist coating layers, residual organic matters present after photoresist development, and the like. See, for instance, U.S. Pat. No. 6,605,417. Such organic layer defects can result in defects in the processed microelectronic device.
To improve photoresist performance, certain photoresist filtration procedures have been reported. See U.S. Pat. No. 6,130,122 and U.S. Published Application 20020187421. Such prior filtration approaches have not been wholly satisfactory, particularly for high-performance photoresists used to form extremely small features such as sub-quarter micron lines.
It would be desirable to have new photoresist and antireflective compositions, including photoresist and antireflective compositions that can produce highly resolved images. It also would be desirable to have methods for preparation of such photoresist and antireflective compositions, particularly where the photoresists and antireflective compositions yielded decreased defect levels upon lithographic processing.